1. Field of the Invention
The present invention generally relates to digital data transmission of video information and more particularly to the delivery of user selected video information to subscribing users.
2. Description of the Prior Art
The mass distribution of video programming signals (i.e., television) was originally accomplished primarily by the broadcasting of a very high frequency (i.e., VHF) carrier containing an amplitude modulated video signal and a frequency modulated audio signal. Through the addition of more broadcasting transmitters, a modest number of different programming signals could be simultaneously distributed to a large number of potential users with a modest capital commitment. Using this technique, the capital commitment increases almost linearly with number of different programming channels within the limits of the available spectrum space for separate and independent carriers.
Within a couple of decades, most of the scarce VHF spectrum space had been committed, and increasing demand for additional programming channels resulted in the allocation of spectrum space in the ultra-high frequency (i.e., UHF) region. Whereas virtually all receivers became UHF compatible, as a matter of policy, and UHF channels were assigned to requesters, it was appreciated that there were no economies of scale through the addition of more broadcast programming channels.
The cable television channel era was the result, wherein a capital commitment was required to wire each user home within a service area. As a result, about one hundred separate programming channels became readily available at a lesser cost than providing the same number of channels using conventional broadcast means. Initially, cable television was simply an analog system in which low power modulated carriers were transferred over a coaxial cable rather than being broadcast into the ether at substantially higher power levels. The cost saving was realized because the broadcasting was accomplished at substantially lower power.
With approximately one hundred different programming channels, it is typical to charge cable service user fees in accordance with a hierarchy of programming channels. The least expensive channels tend to be the preexisting broadcast channels and those cable channels supported primarily by advertisers which are intended for the most general audiences. The subscriber fees to access other channels increase as the programming becomes more specialized, advertising revenue becomes less likely to pay the programming costs, and the programming materials tend to have substantial economic value through other distribution channels. The so-called “premium channels” which show current and/or near current movies without advertising are typical of the higher cost programming options.
Most commercial cable television providers package the various programming channels into programming channel groups with different prices such that a given user can select a suitable programming package and pay the equivalent fee. Typically, a cable provider box, which couples the user television receiver to the coaxial cable source, is controlled by the cable television provider to give access to a given user to only those channels for which the appropriate subscriber fee has been paid.
The most expensive cable television channels currently available are “pay-per-view” or PPV. With the PPV concept, a given user can subscribe to a given programming channel for a single individual program of up to several hours for a separate subscriber fee. Typically, PPV channels provide sporting events and almost current movies.
Perhaps the major disadvantage of the PPV concept as currently implemented, is that the programming is provided in the “broadcast” mode. That means that the programming begins and runs on a predefined schedule. As a result, programming is missed if the user receives a telephone call, for example, during the viewing. Furthermore, it ordinarily requires the user to allocate viewing time to coincide with the predefined schedule. To overcome this disadvantage, many users rent video programs as video cassette recordings (i.e., VCR) from commercial stores which provide such a rental service. This permits the viewer to watch the program in accordance with her/his own schedule, stop the program during interruptions, and replay portions of the program which may not be readily understood. The primary disadvantage of the VCR rental approach is the need to physically go to the rental store to obtain the program and return to the rental store to return the recording.
With the capital commitment for cable television in place, their appear to be substantial new uses for the basic coaxial pathway. Such uses include, telephone, computer modem, facsimile, and video conferencing. To properly coordinate such diverse information transmission activities, attention is being directed to digital transmission schemes which provide for easier management of the distribution resources. U.S. Pat. No. 5,570,355, issued to Dail et al., discusses the handling of a number of diverse information transmissions within a single system. U.S. Pat. No. 5,673,265, issued to Gupta et al., U.S. Pat. No. 5,754,773, issued to Ozden et al., and U.S. Pat. No. 5,799,017, issued to Gupta et al., all discuss multi-media distribution systems. U.S. Pat. No. 5,555,244, issued to Gupta et al., is directed to multimedia distribution to residential users.
The digitization of video results in a great deal of data which must be transferred at a high rate to yield acceptable performance and resolution. By current standards, 3 mbits/sec. is considered to be a very acceptable rate. Such high data rates require systems which can provide high data rate transmission. U.S. Pat. No. 5,724,543, issued to Ozden et al., U.S. Pat. No. 5,699,362, issued to Makam, and U.S. Pat. No. 5,826,110, issued to Ozden et al., all concern themselves with high data rate retrieval and transmission. U.S. Pat. No. 5,675,573, issued to Karol et al., discusses the management of high data rate bandwidths.
In addition to retrieval and transmission of the required high data rates, there is also the need to provide high speed switching for switching as between data sources and destinations. U.S. Pat. No. 5,751,704, issued to Kostic et al., and U.S. Pat. No. 5,740,176, issued to Gupta et al., discuss high speed digital switching systems.
Whether it is data storage and retrieval, data transmission, or data switching, the fundamental technological problem associated with digital video results from the sheer volume of digitized video data and the tremendous rate at which it must be provided to the ultimate user for satisfactory performance. One technique for reduction of the volume problem is in reducing the resolution (and hence the volume of data) for those applications for which such reduction is acceptable. U.S. Pat. No. 5,623,308 and U.S. Pat. No. 5,691,768, both issued to Civanlar et al., directly address the handling of multiple resolution digitized video signals within a single system.
Notwithstanding attempts to reduce the resolutions to the lowest acceptable levels, the total data volume of any commercially useful system will remain high. The most common way to treat extremely high data volumes is through data compression. U.S. Pat. No. 5,710,829, issued to Chen et al., U.S. Pat. No. 5,742,343, issued to Haskell et al., and U.S. Pat. No. 5,619,256, issued to Haskell et al., are concerned with digital compression techniques. Specific attention to compression of digitized video is found in U.S. Pat. No. 5,764,803, issued to Jacquin et al. Compression of 3-dimensional images is treated by U.S. Pat. No. 5,612,735, issued to Haskell et al.
The evolving techniques of digitized video transmission have resulted in a transmission standard, called Asynchronous Transfer Mode (ATM). U.S. Pat. No. 5,668,841, issued to Haskell et al., describes data transmission using the ATM standard. An ATM converter is discussed in U.S. Pat. No. 5,809,022, issued to Byers et al. U.S. Pat. No. 5,724,349, issued to Cloonan et al., suggests an approach to packet switching within an ATM system. An ATM architecture is discussed in U.S. Pat. No. 5,781,320, issued to Byers. Interfacing to ATM systems is addressed in U.S. Pat. No. 5,842,111, issued to Byers.
A solution to the PPV problems noted above utilizing digitized video has been termed, Video on Demand (or VOD). In a VOD system, digitized video programming is made available to individual cable television subscribers in response to specific requests made by the user. U.S. Pat. No. 5,867,155, issued to Williams, describes the use of VOD for a very specialized application. Sea Change, International, has proposed a VOD approach for cable television subscribers. U.S. Pat. No. 5,583,561, issued to Baker et al., assigned to the assignee of the present invention and incorporated herein by reference, discloses and teaches a complete, modem VOD system employing a centralized architecture utilizing an enterprise server developed by Unisys Corporation.
To fully utilize VOD for commercially useful subscriber levels, substantial administrative message traffic is required between the subscribers and the central controlling site(s). For current PPV, this typically takes the form of telephone communication with the subscriber. This is acceptable for PPV only because the total programming selections and timing are so limited. However, VOD on demand so increases the options available to the subscriber, such manual attention is impractical.
To efficiently utilize the resources of the VOD system requires a methodology for transferring programming materials (or assets) from long term storage (i.e., disk) to an appropriate memory space and initiating streaming from an appropriate video server. When an asset is requested which is already being streamed, no additional transfer is required, if the associated video server has sufficient capacity to also stream the asset for the new request.